U.S. patent number 7,420,134 [Application Number 11/725,185] was granted by the patent office on 2008-09-02 for fluid level switch.
This patent grant is currently assigned to ITT Manufacturing Enterprises, Inc. Invention is credited to Frank Mark Domzalski, Kevin J. Leary.
United States Patent |
7,420,134 |
Leary , et al. |
September 2, 2008 |
Fluid level switch
Abstract
The present invention provides a float level switch featuring a
housing; an actuator shaft arranged in the housing; and a low force
shaft seal assembly arranged between the actuator shaft and the
housing, having a combination of disks or seals, one being made of
a semi-rigid lubricious material, for maintaining a watertight seal
with a substantially reduced rotational force or friction on the
actuator shaft than a conventional O-ring.
Inventors: |
Leary; Kevin J. (Hamilton,
MA), Domzalski; Frank Mark (Wellesley, MA) |
Assignee: |
ITT Manufacturing Enterprises,
Inc (Wilmington, DE)
|
Family
ID: |
39718385 |
Appl.
No.: |
11/725,185 |
Filed: |
March 15, 2007 |
Current U.S.
Class: |
200/84R;
200/61.21 |
Current CPC
Class: |
H01H
35/18 (20130101) |
Current International
Class: |
H01H
35/18 (20060101) |
Field of
Search: |
;200/61.2,61.21,84R-84C
;73/305-309,313,317,318,322.5 ;340/604,605,623,625 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Friedhofer; Michael A
Claims
We claim:
1. A float level switch comprising: a housing; an actuator shaft
arranged in the housing; and a low force shaft seal assembly
arranged between the actuator shaft and the housing, having a
combination of disks or seals, one being made of a semi-rigid
lubricious material, for maintaining a watertight seal with a
substantially reduced rotational force or friction on the actuator
shaft than a conventional O-ring, wherein the low force shaft seal
assembly comprises: a seal cup coupled to the housing; an inboard
disk or seal arranged between the seal cup and the actuator shaft
and being made of the semi-rigid lubricious material; an outboard
disk or seal coupled between the inboard disk or seal and the
actuator shaft and being made of rubber; and a retaining ring
arranged between the outboard disk or seal and the seal cup for
frictionally engaging the outboard disk or seal and holding it in
place.
2. A float level switch according to claim 1, wherein the one disk
or seal is made of a fluoropolymer (i.e. Teflon) or other suitable
semi-rigid lubricious material.
3. A float level switch according to claim 1, wherein the actuator
shaft is coupled to a buoyant paddle that is allowed to raise and
lower by pivoting about an actuator axis.
4. A float level switch according to claim 3, wherein the float
level switch comprises a cover arranged thereon for protecting the
buoyant paddle, and a cantilevered test lever coupled to the
buoyant paddle for testing the float level switch when the cover is
arranged thereon.
5. A float level switch comprising: a switch assembly having a base
with one or more projections extending outwardly from opposing side
walls; and a detachable mounting plate having a recessed portion
with one or more corresponding projections extending inwardly from
opposing side walls for receiving the projections of the switch
assembly for frictionally engaging and detachably coupling the
switch assembly to the detachable mounting plate when the base of
the switch assembly is arranged in the recessed portion of the
detachable mounting plate so as to be able to detach the switch
assembly from the detachable mounting plate by applying a suitable
force to the switch assembly.
6. A float level switch according to claim 5, wherein the mounting
plate has one or more release levers.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a switch; and more particularly to
a fluid level switch to sense changes in liquid levels.
2. Brief Description of Related Art
Paddle-type fluid level switches have historically used Mercury
tubes to sense changes in liquid level and to provide the switch in
an electrical circuit. Recent concerns about the health and
environment impacts of Mercury have required a change in paddle
switch technology.
One known float switch utilizes a snap switch having O-rings for
the shaft seal. O-ring shaft seals, however, can impart high
friction forces to the rotating shaft, which reduces the amount of
buoyant force available to actuate the snap switch, and
gravitational force available to reset the switch. These friction
losses make the product less robust.
Moreover, a search was conducted in the United States Patent and
Trademark Office and the following patents were developed by the
searcher includes the following with a brief description
thereof:
Different Float Structures
U.S. Pat. Nos. 3,621,168, 4,600,820, 4,848,151 and 5,814,780 show
different float structures and are summarized as follows: The '168
patent discloses a switching device that uses electrical leads as a
flexible member to eliminate the need for a hinge between a float
24 and a fixed structure. The '820 and '151 patents disclose an
electrical cut off float switch having a balance float assembly
with a counterweight and a solid float member pivoted on a pivot
point. The '780 patent discloses a pivotable float switch inside a
housing having a float with a float body and pivot arms coupled in
pivot apertures in the housing.
Different Sealed Switches
U.S. Pat. Nos. 2,885,507, 3,890,478, 3,908,107 and 5,374,790 show
different sealed switches and are summarized as follows: The '507
patent discloses a level indicator having a float supported on a
pivot coupled to a switch actuator rod coupled via a pivot to a
compartment. The '478 patent discloses a liquid level sensor having
a float with an arm pivoted by a pin to a diaphragm, as well as a
float having an arm coupled via retainers to a diaphragm. The '107
patent discloses a device for the control of a liquid level in a
receptacle having a float mounted on a level arm and urged and
pivoted on a bearing inside a refill container. The '790 patent
discloses a liquid level switch assembly having a float mounted on
a float arm rotatably mounted a pivot axle.
Other Switches
U.S. Pat. Nos. 4,084,073, 4,746,776 6,254,351, 6,729,847 show other
types of switches and are summarized as follows: The '073 patent
discloses a float-type pump control switch for a submersible pump,
having an activator arm pivotally mounted within a housing that
floats up and down based on the level of the fluid in the sump and
turn on and off based on the angle of the float. The '776 patent
discloses a float-actuated switching assembly having a float
mounted on a movable cam that passes though a mounting member via
an aperture and fitting. The '351 patent discloses a snap-action
float assembly having a float assembly that rotates on a pivot axis
inside a fluid reservoir. The '847 patent discloses a bilge pump
seal and float actuator having a float coupled to an actuator that
extends through an aperture of an interior wall, and having a seal
and a sealing disk located within the aperture thereby sealing the
same.
SUMMARY OF THE INVENTION
In its broadest sense, the present invention features a new and
unique float level switch featuring a housing; an actuator shaft
arranged in the housing; and a low force shaft seal assembly
arranged between the actuator shaft and the housing, having a
combination of disks or seals, one of the disks or seals being made
of a semi-rigid lubricious material, for maintaining a watertight
seal with a substantially reduced rotational force or friction on
the actuator shaft than a conventional O-ring.
In a preferred embodiment, the low force shaft seal assembly may
include a seal cup coupled in relation to the housing; an inboard
disk or seal arranged between the seal cup and the actuator shaft
and being made of the semi-rigid lubricious material; an outboard
disk or seal coupled between the inboard disk or seal and the
actuator shaft and being made of rubber; and a retaining ring
arranged between the outboard disk or seal and the seal cup for
frictionally engaging the outboard disk or seal and holding it in
place.
The inboard disk or seal made of a fluoropolymer (i.e. Teflon) or
other suitable semi-rigid lubricious material slides easily on the
shaft and acts to present only a single edge of the second outboard
(rubber) disk or seal to the rotating shaft surface.
The actuator shaft may be coupled to a buoyant paddle that is
allowed to raise and lower by pivoting about an actuator axis; or
rotational motion of the actuator shaft may actuate a snap switch
located inside a switch base of the float level switch; or the
float level switch may include a cover arranged thereon for
protecting the buoyant paddle, and a cantilevered test lever may be
coupled to the buoyant paddle for testing the float level switch
when the cover is arranged thereon; or some combination of the
aforementioned features.
In an alternative part of the disclosure, the float level switch
may include a switch assembly having one or more projections; and a
detachable mounting plate having one or more corresponding
projections for receiving the projections of the switch assembly
for frictionally engaging and detachably coupling the switch
assembly to the detachable mounting plate so as to be able to
detach the switch assembly from the detachable mounting plate by
applying a suitable force to the switch assembly. The mounting
plate may have one or more release levers.
In summary, the present invention provides a new paddle switch that
incorporates the following novel features:
1) A low force seal--The shaft seal uses two washers, one made of
Buna Rubber and the other of Teflon. The resulting arrangement
results in a watertight seal with the low shaft friction than
conventional O-Rings
2) A Detachable Mounting Plate--Although bilge pumps commonly come
with detachable mounting bases; bilge switches with detachable
mounting plates are previously unknown.
3) A cantilevered test switch--One switch embodiment includes a
cover for protecting the switch paddle. The cover makes testing the
switch difficult. Existing art involves a knob sticking out the
side of the housing. An improved configuration disclosed herein
uses a cantilevered test lever.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a diagram of a fluid level switch according to the
present invention.
FIG. 2 shows a low-force shaft seal in a switch base of the fluid
level switch shown in FIG. 1.
FIG. 3 shows an exploded view of the low-force shaft seal shown in
FIG. 2.
FIG. 4 shows an exploded view of the low-force shaft seal shown in
FIG. 2.
FIG. 5 shows a switch assembly detached from the mounting plate
consistent with that shown in FIG. 1.
FIG. 6 shows a cantilevered test lever according to the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of a fluid level switch generally
indicated as 10 having a switch assembly 12 detachably mounted on a
mounting plate 14. The switch assembly 12 has a paddle 16 that is
buoyant and is allowed to raise and lower by pivoting about an
actuation axis. The rotational motion turns a shaft which actuates
a snap switch located inside a switch base 18 and sends an
electrical signal via an electrical connection 19.
FIG. 2 shows a low-force shaft seal according to the present
invention shown in the form of seal disks generally indicated as 22
in relation to an actuator shaft 24 inside a housing 25 of the
switch base 18. The low-force shaft seal is arranged in relation
to, or may be understood to include, a seal cup 26 and a retaining
ring 28, as shown. The actuation axis is oriented along, and takes
the form of, the longitudinal axis of the actuator shaft 24.
FIG. 3 shows an exploded view of the low-force shaft seal, which is
comprised of an inboard disk 22a made of a semi-rigid, lubricious
material, such as Fluoropolymer or other suitable semi-rigid,
lubricious material either now known or later developed in the
future, and an outboard disk 22b made of rubber or other suitable
elastic material either now known or later developed in the
future.
FIG. 4 shows a cross-section of the low-force shaft seal, which has
an overlapping configuration as shown that limits contact between
the metal actuator shaft 24 and the rubber seal 22b. As shown, the
overlapping configuration includes disks 22a, 22b arranged inside
the seal cup 26 in relation to, and forming sealing contact with,
the actuator shaft 24, and retained in place by the retaining ring
28. The seal cup 26 is arranged inside the housing 25 of the switch
base 18 as shown. The disks 22a, 22b are suitably dimensioned to
flex in relation to the actuation shaft 24 to provide the low-force
shaft sealing. Embodiments are envisioned using different types of
dimensioning to achieve the desired flexing, and the scope of the
invention is not intended to be limited to any particular
dimensioning to achieve the same. This overlapping configuration
maintains a watertight seal, but reduces rotational force from the
seal on the actuator shaft 24.
FIG. 5 shows the switch assembly 12 having a base 13 with one or
more projections 12a extending outwardly from opposing side walls
13a that is detached from the mounting plate 14 having a recessed
portion 15 with one or more corresponding projections extending
inwardly from opposing side walls 15a when the base 15 of the
switch assembly 12 is arranged in the recessed portion 15 of the
mounting plate 14. In operation, the switch assembly 12 and the
mounting plate 14 are coupled together by applying a suitable force
to, and snapping the one or more projections 12a over and into the
one or more corresponding projections 14a for frictionally engaging
the same. In order to remove the switch assembly 12 from the
mounting plate 14, a corresponding suitable force is applied. The
detachable mounting plate 14 also has one or more release levers
14b for gripping the mounting plate 14.
The detachable mounting plate 14 may be affixed to a surface by one
or more screws 40, 42.
The detachable mounting plate 14 allows the use of a standardized
switch module in all models of a product line. It also allows a
wide variety of mounting options.
The scope of the invention is intended to include embodiments
utilizing one release lever or even no release levers. For example,
embodiments are envisioned in which the switch housing is pushed to
one side and tilted out the opposite side of the base.
The Cantilevered Test Lever
FIG. 6 shows another improvement of the present invention in the
form of a cantilevered test lever generally indicated as 100, where
the mounting base is separate and attached via a snap fit.
The switch embodiment shown in FIG. 6 also includes a cover 102 for
protecting a switch paddle 110. The cover 102 makes testing the
switch difficult. As shown, the cantilevered test lever 100 may be
pressed downwardly to test the switch paddle 110.
Known devices in the prior art focuses on side-mounted knobs to
rotate the switch float that is otherwise shrouded by a float
guard. The cantilevered test lever 100 shown here is more
convenient and robust than existing solutions.
The Scope of the Invention
It should be understood that, unless stated otherwise herein, any
of the features, characteristics, alternatives or modifications
described regarding a particular embodiment herein may also be
applied, used, or incorporated with any other embodiment described
herein. Also, the drawings herein are not drawn to scale.
Although the invention has been described and illustrated with
respect to exemplary embodiments thereof, the foregoing and various
other additions and omissions may be made therein and thereto
without departing from the spirit and scope of the present
invention.
* * * * *